I bought 3 plants of Lindheimer's sennae, sennae lindenheimerina, in hopes
of obtaining eggs to record a life history of Cloudless Sulphurs. The plan
worked like a charm: long before the plants were set in the ground, I found
sulphur eggs on them. The surprise came a couple of weeks into the study: I
realized I was raising two kinds of caterpillars. Of the three eggs I collected,
two were Cloudless Sulphurs, but the other was a Sleepy Orange.

This was disturbing, because it would have ruined the study if I could not
distinguish which caterpillars were which. I went back and reviewed photos.
Fortunately, it was easy to separate the Sleepy Orange caterpillar from the
other two. Its first instar was a pale white, and second or third pale green,
while the Coudless Sulphurs were a strong yellow throughout this period. In
later instars, differences in color and striping were equally obvious.

The young sennae caterpillars favored flowers, and blended in very well
(see 9-10-10 picture). The older caterpillars moved to the leaves, perhaps of
necessity, and became green as their diet changed.

One of the presumed sennae eggs was white when found, indicating it had
been deposited within a day or two. This suggests the caterpillars eclosed on
the third or fourth day after the eggs were laid. The first caterpillar pupated
on September 19, after 12 days, and the adult emerged six days later. It
therefore required just over three weeks to go from egg to adult. The second
caterpillar took three days longer to pupate and emerge.